1. Field of the Invention
The Present invention relates to an apparatus for detecting the number of a track traverse on an optical disk, and more particularly, to an apparatus for detecting the number of the track traverse on an optical disk, which is capable of improving a speed of detecting the number of the track traverse.
2. Discussion of Related Art
In general, a disk playback apparatus used for reproducing information written on a digital audio disk is constructed to reproduce a program information placed on a temporary position by using an address information or a TOC (Table of Content) on a disk.
In this disk playback apparatus, data inputted to the disk in a unit of track is reproduced in sequence. However, there is a case that according to a necessity and by an intention of a user, he/she wants to select a desired temporary spot on the disk in order to reproduce the address information on the selected spot, instead of reproducing in a recorded sequence the program information that is in the disk. Like this, in the case of reproducing the address information on the desired temporary spot of the disk, it requires such an operation that the selected spot is determined as the pick-up position by a pick-up means. Such operation for determining the pick-up position is generally defined as a search operation.
A track search operation in a conventional optical disk playback apparatus is described as follows:
First, the pick-up position by the pick-up means is rapidly moved by a given distance in a direction of crossing a written track of the disk, and then, a normal playback state becomes to thus pick up the address information. Subsequently, the pick-up position by the pick-up means is obtained from the picked-up address information, and an operation for obtaining a difference between the pick-up position and a target position is performed repeatedly till the target spot is searched. That is, for moving the pick-up means at a high speed, the pick-up operation of picking up the address information is performed, thereby executing intermittently an operation that the pick-up position by the pick-up means is rapidly moved by a given distance in a direction of crossing the written track of the disk and then to gradually close to the target spot.
However, in such conventional track search operation, the address information should be picked up in the midst of the rapid movement to the pick-up position by each pick-up means to obtain a current position and a difference between the current position and the target position. Therefore, conventional track search operation had a difficulty in achieving a high-speed search.
Meantime, in other method of searching the tracks of an optical disk, a track traverse signal is detected from a track within the optical disk to count the number of tracks on which an optical head traverses, and the counted numbers are used as a reference for a moving distance of the optical head to the target position. However, when the optical head moves rapidly for a high-speed search, there occurs a case that the optical head is not passed on a pit array provided within the disk track to detract an accuracy of the track traverse signal. Such phenomenon occurs particularly seriously when frequency of the track traverse signal is ⅓ or more of signal frequency of the optical disk in proportion to the moving speed of the optical head, which cause a serious intermittence of the track traverse signal.
Therefore, in order to realize a stabilized slide jump capable of settling the above problems, the moving speed of the optical head is limited, or instead of the track signal, a signal generated from equipment as a specific scale is used as the reference signal for the moving distance of the optical head. But, in the former case, a slide jump time is lengthened relatively, and in the later case, an accurate track movement is difficult due to a limitation of an accuracy of the scale.
FIG. 1 shows an apparatus for detecting the number of the track traverse on the optical disk according to a conventional method, in which another search operation is described.
Referring to FIG. 1, a data signal read by a general pick-up means in a movement of an optical head is transferred to a bandpass filter 1 to eliminate a low DC component, a high frequency component and noise. The data signal passed through the bandpass filter 1 is inverted in its polarity by an inverter 2, subsequently is passed through a first amplifier 3, a first diode D1, a second amplifier 4, a first capacitor C1, a first resistance R1, a second capacitor C2 and a second resistance R2, and then outputted to an output terminal a. The data signal inverted in its polarity by the inverter 2 is also outputted to an output terminal b via a third amplifier 5, a second diode D2, a forth amplifier 6, a third capacitor C3, a third resistance R3, a forth capacitor C4 and a forth resistance R4.
Subsequently, the data signals outputted to the output terminal a, b are calculated for a difference therebetween in a subtracter 7 and the number of the traversed tracks is then counted in a counter 8. Though, it is not shown in the drawing, the counted number of the traversed tracks is sent to a controller performing a search operation.
FIG. 2 depicts waveform of an output signal detected in the output terminal a, b versus the inputted data signal, in the apparatus for detecting the number of the track traverse on the optical disk in FIG. 1. In the apparatus for detecting the number of the track traverse on the disk, generally a charge is performed by the inputted data signal, and a discharge is performed by a capacitor and a resistance(τ=RC, in which τ is a discharge rate).
At this time, in the case of trying to increase the discharge rate by decreasing τ, as shown in FIG. 3, it is apparent that the waveform of the output signal detected in the output terminals a, b is very unstable in comparison with an ideal result. In the case of trying to decrease the discharge rate by increasing τ, as shown in FIG. 4, it can be understood that the waveform of the output signal detected in the output terminal a, b is very unstable.
As described above and shown FIGS. 3 and 4, in the conventional method, the output waveform of the output terminals is unstable when the jumping speed is increased to perform a high speed search. That is, a subtraction of the data signals through the subtracter is impossible since the output waveform of the output terminal is unstable. Therefore, the high-speed search for the number of the track traverse on the optical disk is difficult.